Brannigan on Mendel
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The Reification of Mendel Author(s): Augustine Brannigan Source: Social Studies of Science, Vol. 9, No. 4 (Nov., 1979), pp. 423-454 Published by: Sage Publications, Ltd. Stable URL: http://www.jstor.org/stable/284572 Accessed: 15-01-2017 23:58 UTC REFERENCES Linked references are available on JSTOR for this article: http://www.jstor.org/stable/284572?seq=1&cid=pdf-reference#references_tab_contents You may need to log in to JSTOR to access the linked references. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at http://about.jstor.org/terms Sage Publications, Ltd. is collaborating with JSTOR to digitize, preserve and extend access to Social Studies of Science This content downloaded from 136.159.235.223 on Sun, 15 Jan 2017 23:58:57 UTC All use subject to http://about.jstor.org/terms * ABSTRACT A re-examination of the case of Mendel suggests that he was neither ignored in the 1860s nor simply re-discovered in 1900. In 1900, the concern for priority among De Vries, Correns and Tschermak, and the controversy between Bateson and the biometricians over species variation, led scientists to reconstruct the relevance of Mendel's hybridization experiments with Pisum in terms of their own work on natural selection. By contrast, an examination of the original paper indicates Mendel's concern, not with variability, but with the very process of speciation via hybridization. The Reification of Mendel Augustine Brannigan The case of Gregor Mendel presents one of the great perennial pro- blems in the history of genetics. How could a series of outstanding experiments which were conducted over a period of years and which laid the foundation for the modern field of genetics fail to have come to the attention of the scientific community? A series of historical papers has tried to account for the 'long neglect' of Mendel's work by drawing attention to such things as the forbid- ding mathematical approach, the obscurity of the publication, the low status of the researcher, the prematurity of the problem and the misinterpretation of the results. None of these solutions is com- pletely convincing. The present paper offers an alternative hypothesis: that the relevance of Mendel's achievement changed over time from the point at which it was initially conducted in the 1850s and 60s to the point at which it reappeared in 1900. Specifically, it is suggested that Mendel's revival in 1900 took place in the context of a priority dispute between Correns and De Vries, and that this dispute led scientists to overlook the original intent of Social Studies of Science (SAGE, London and Beverly Hills), Vol. 9 (1979), 423-54 This content downloaded from 136.159.235.223 on Sun, 15 Jan 2017 23:58:57 UTC All use subject to http://about.jstor.org/terms 424 Social Studies of Science the earlier research. Furthermore, the revival of Mendel in England emerged in the context of a controversy between the biometricians who had adopted a model of continuous variation and evolution by the selection of individual differences, and the 'saltationists' like William Bateson who had adopted the model of evolution by the selection of 'mutations' or discontinuous variations. In the context of this controversy, Mendel's work was erroneously employed to dismiss biometrical models of inheritance and to underwrite the ef- forts of the mutationists. However inaccurate such positions turned out to be, Mendel's achievement emerged at a point in time when the problem of inheritance was an acute question in evolutionary theory, especially in light of Darwin's failing model of pangenesis. On the other hand, it appears that, in his own day, Mendel's work was undertaken in the tradition of the hybridists who viewed the process of inheritance not as a subfield in the general theory of evolution but as itself a potential explanation of the origin of species. These facts tend to support the opinion that in 1866 Mendel's work figured as normal science in the hybridist tradition, while in 1900 the revival of Mendel's discovery of segregation con- stituted a relatively revolutionary achievement.' The Contexts of Mendel's Revival In 1900 Hugo De Vries announced the results of his experiments describing 'the law of segregation of hybrids.' That law was based on De Vries' reformulation of the Darwinian hypothesis of pangenesis presented in his Intracellular Pangenesis (1899). De Vries divided Darwin's hypothesis into two parts: a material unit hypothesis which held that qualities inherited by the organism are represented by discrete material particles in the germ cell, and a transportation hypothesis which held that parts of the organism throw off particles which often become incorporated into the germ cell, and result in the inheritance of changes acquired during on- togenetic experiences. However, De Vries dismissed the transporta- tion hypothesis on the grounds that it was not empirically sup- ported. August Weismann had as early as 1883 propounded the theory of the absolute independence of the germ plasma from the other somatic cells; and prior to this, Francis Galton's transfusion experiments had thrown doubt on the existence of mobile 'gem- mules' and their effects on the germ plasma and inheritance. Con- This content downloaded from 136.159.235.223 on Sun, 15 Jan 2017 23:58:57 UTC All use subject to http://about.jstor.org/terms Brannigan: Reification of Mendel 425 sequently, De Vries' reformulation of Darwin's provisional hypothesis focused exclusively on the existence of discrete particles of inheritance. De Vries undertook a programme of experimentation during the 1 890s to explore the behaviour of these particles during the process of inheritance. However, his chief interest in these experiments was to determine the process by which species emerged. In De Vries' mind, the most important hereditary solution to this problem was the process of mutation. From at least 1886, when he discovered new species of evening primrose in a field near Hilversum, De Vries had entertained the hypothesis that speciation occurs through the appearance of new species by discontinuous variations of traits. De Vries concluded that the new species of primrose (Oenethera lamar- ckiana) found side by side with the traditional but markedly dissimilar form of the same species had appeared as a result of a mutation.2 During the decade prior to his segregation paper, he conducted large numbers of hybrid experiments with over 30 species, in which he observed the 'splitting' or segregation of monohybrids in, for example, opium poppies and oenethera lamar- ckiana; second generation hybrids characteristically reverted to a recessive character in about one quarter of the plants. It was his conjecture during this period that evolution resulted from what he termed 'progressive mutations' - that is to say, by mutations in which the effect of an 'active pangen' was not held in check by a 'semi-latent pangen.'3 Different populations presumably could be described in terms of the activity or latency of the pangens and hence classified according to their mutability. Since De Vries was most interested in the origin of species, progressive mutations (that is, mutations which has arisen without 'antagonistic pangens') were of far more interest to him than hybrids characterized by segrega- tion and reversion to parental stocks. Consequently, though De Vries clearly recognized the ratio of dominance and the principle of gametic segregation, these were of secondary interest in his Muta- tion Theory, which he published in 1901-03. Nonetheless, he published his law of the segregation of hybrids, which specified two important conclusions:4 1. Of the two antagonistic characteristics, the hybrid carries only one, and that in complete development. Thus in this respect the hybrid is indistinguishable from one of the two parents. There are no transitional forms. 2. In the formation of pollen and ovules, the two characteristics separate, following for the most part simple laws of probability. This content downloaded from 136.159.235.223 on Sun, 15 Jan 2017 23:58:57 UTC All use subject to http://about.jstor.org/terms 426 Social Studies of Science Actually, De Vries wrote three articles announcing his conclu- sions. His first communication was published in Comptes Rendus de LAcademie des Sciences at Paris. Here De Vries made no men- tion of the fact that his laws of segregation and ratios of dominance were identical to the conclusions of a certain Gregor Mendel which were published 34 years earlier. However, in a more extended report which appeared in May, and which had actually been the first of the three reports to be prepared, De Vries noted that 'these two statements in their most essential points, were drawn up long ago by Mendel for a special case (peas).'S In a footnote he sug- gested that 'this important treatise is so seldom cited that I first learned of its existence after I had completed the majority of my ex- periments and deduced from them the statements communicated in the text.'6 Exactly how seldom was Mendel cited? The Mendel Citations Mendel's paper on Pisum was cited several times in different places prior to its wide acclamation in 1900. In 1869 it was quoted in Her- mann Hoffmann's Untersuchungen zur Bestimmung des Werthes von Species und Varietat. Mendel's conclusions were summarized as follows: 'Hybrids possess the tendency in the succeeding genera- tions to revert to the parent species.'7 One finds a similar inter- pretation in the second major book to appear, Die Pflanzenmishl- inge by W.